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      <td width="400px"><p class="toc level1"><a href="docinfo.html">Document Information</a></p>
<p class="toc level1 tocsp"><a href="gexaf.html">Preface</a></p>
<p class="toc level1 tocsp"><a href="gfirp.html">Part&nbsp;I&nbsp;Introduction</a></p>
<p class="toc level2"><a href="bnaaw.html">1.&nbsp;&nbsp;Overview</a></p>
<p class="toc level2"><a href="gfiud.html">2.&nbsp;&nbsp;Using the Tutorial Examples</a></p>
<p class="toc level1 tocsp"><a href="bnadp.html">Part&nbsp;II&nbsp;The Web Tier</a></p>
<p class="toc level2"><a href="bnadr.html">3.&nbsp;&nbsp;Getting Started with Web Applications</a></p>
<p class="toc level2"><a href="bnaph.html">4.&nbsp;&nbsp;JavaServer Faces Technology</a></p>
<p class="toc level2"><a href="giepx.html">5.&nbsp;&nbsp;Introduction to Facelets</a></p>
<p class="toc level2"><a href="gjddd.html">6.&nbsp;&nbsp;Expression Language</a></p>
<p class="toc level2"><a href="bnaqz.html">7.&nbsp;&nbsp;Using JavaServer Faces Technology in Web Pages</a></p>
<p class="toc level2"><a href="gjcut.html">8.&nbsp;&nbsp;Using Converters, Listeners, and Validators</a></p>
<p class="toc level2"><a href="bnatx.html">9.&nbsp;&nbsp;Developing with JavaServer Faces Technology</a></p>
<p class="toc level2"><a href="gkmaa.html">10.&nbsp;&nbsp;JavaServer Faces Technology Advanced Concepts</a></p>
<p class="toc level2"><a href="bnawo.html">11.&nbsp;&nbsp;Configuring JavaServer Faces Applications</a></p>
<p class="toc level2"><a href="gkiow.html">12.&nbsp;&nbsp;Using Ajax with JavaServer Faces Technology</a></p>
<p class="toc level2"><a href="gkhxa.html">13.&nbsp;&nbsp;Advanced Composite Components</a></p>
<p class="toc level2"><a href="bnavg.html">14.&nbsp;&nbsp;Creating Custom UI Components</a></p>
<p class="toc level2"><a href="bnafd.html">15.&nbsp;&nbsp;Java Servlet Technology</a></p>
<p class="toc level2"><a href="bnaxu.html">16.&nbsp;&nbsp;Internationalizing and Localizing Web Applications</a></p>
<p class="toc level1 tocsp"><a href="bnayk.html">Part&nbsp;III&nbsp;Web Services</a></p>
<p class="toc level2"><a href="gijti.html">17.&nbsp;&nbsp;Introduction to Web Services</a></p>
<p class="toc level2"><a href="bnayl.html">18.&nbsp;&nbsp;Building Web Services with JAX-WS</a></p>
<p class="toc level2"><a href="giepu.html">19.&nbsp;&nbsp;Building RESTful Web Services with JAX-RS</a></p>
<p class="toc level2"><a href="gjjxe.html">20.&nbsp;&nbsp;Advanced JAX-RS Features</a></p>
<p class="toc level2"><a href="gkojl.html">21.&nbsp;&nbsp;Running the Advanced JAX-RS Example Application</a></p>
<p class="toc level1 tocsp"><a href="bnblr.html">Part&nbsp;IV&nbsp;Enterprise Beans</a></p>
<p class="toc level2"><a href="gijsz.html">22.&nbsp;&nbsp;Enterprise Beans</a></p>
<p class="toc level2"><a href="gijre.html">23.&nbsp;&nbsp;Getting Started with Enterprise Beans</a></p>
<p class="toc level2"><a href="gijrb.html">24.&nbsp;&nbsp;Running the Enterprise Bean Examples</a></p>
<p class="toc level2"><a href="bnbpk.html">25.&nbsp;&nbsp;A Message-Driven Bean Example</a></p>
<p class="toc level2"><a href="gkcqz.html">26.&nbsp;&nbsp;Using the Embedded Enterprise Bean Container</a></p>
<p class="toc level2"><a href="gkidz.html">27.&nbsp;&nbsp;Using Asynchronous Method Invocation in Session Beans</a></p>
<p class="toc level1 tocsp"><a href="gjbnr.html">Part&nbsp;V&nbsp;Contexts and Dependency Injection for the Java EE Platform</a></p>
<p class="toc level2"><a href="giwhb.html">28.&nbsp;&nbsp;Introduction to Contexts and Dependency Injection for the Java EE Platform</a></p>
<p class="toc level2"><a href="gjbls.html">29.&nbsp;&nbsp;Running the Basic Contexts and Dependency Injection Examples</a></p>
<p class="toc level2"><a href="gjehi.html">30.&nbsp;&nbsp;Contexts and Dependency Injection for the Java EE Platform: Advanced Topics</a></p>
<p class="toc level2"><a href="gkhre.html">31.&nbsp;&nbsp;Running the Advanced Contexts and Dependency Injection Examples</a></p>
<p class="toc level1 tocsp"><a href="bnbpy.html">Part&nbsp;VI&nbsp;Persistence</a></p>
<p class="toc level2"><a href="bnbpz.html">32.&nbsp;&nbsp;Introduction to the Java Persistence API</a></p>
<p class="toc level2"><a href="gijst.html">33.&nbsp;&nbsp;Running the Persistence Examples</a></p>
<p class="toc level2"><a href="bnbtg.html">34.&nbsp;&nbsp;The Java Persistence Query Language</a></p>
<p class="toc level2"><a href="gjitv.html">35.&nbsp;&nbsp;Using the Criteria API to Create Queries</a></p>
<p class="toc level2"><a href="gkjiq.html">36.&nbsp;&nbsp;Creating and Using String-Based Criteria Queries</a></p>
<p class="toc level2"><a href="gkjjf.html">37.&nbsp;&nbsp;Controlling Concurrent Access to Entity Data with Locking</a></p>
<p class="toc level2"><a href="gkjia.html">38.&nbsp;&nbsp;Improving the Performance of Java Persistence API Applications By Setting a Second-Level Cache</a></p>
<p class="toc level1 tocsp"><a href="gijrp.html">Part&nbsp;VII&nbsp;Security</a></p>
<p class="toc level2"><a href="bnbwj.html">39.&nbsp;&nbsp;Introduction to Security in the Java EE Platform</a></p>
<p class="toc level2"><a href="bncas.html">40.&nbsp;&nbsp;Getting Started Securing Web Applications</a></p>
<p class="toc level2"><a href="bnbyk.html">41.&nbsp;&nbsp;Getting Started Securing Enterprise Applications</a></p>
<p class="toc level1 tocsp"><a href="gijue.html">Part&nbsp;VIII&nbsp;Java EE Supporting Technologies</a></p>
<p class="toc level2"><a href="gijto.html">42.&nbsp;&nbsp;Introduction to Java EE Supporting Technologies</a></p>
<p class="toc level2"><a href="bncih.html">43.&nbsp;&nbsp;Transactions</a></p>
<p class="toc level2"><a href="bncjh.html">44.&nbsp;&nbsp;Resource Connections</a></p>
<p class="toc level3"><a href="bncji.html">Resources and JNDI Naming</a></p>
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<p class="toc level3"><a href=""><tt>DataSource</tt> Objects and Connection Pools</a></p>
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<p class="toc level3"><a href="bncjk.html">Resource Injection</a></p>
<p class="toc level4"><a href="bncjk.html#bncjl">Field-Based Injection</a></p>
<p class="toc level4"><a href="bncjk.html#bncjm">Method-Based Injection</a></p>
<p class="toc level4"><a href="bncjk.html#bncjn">Class-Based Injection</a></p>
<p class="toc level3 tocsp"><a href="gipgl.html">Resource Adapters and Contracts</a></p>
<p class="toc level4"><a href="gipgl.html#gipgy">Management Contracts</a></p>
<p class="toc level5"><a href="gipgl.html#gipht">Lifecycle Management</a></p>
<p class="toc level5"><a href="gipgl.html#gipig">Work Management Contract</a></p>
<p class="toc level4 tocsp"><a href="gipgl.html#gipmk">Generic Work Context Contract</a></p>
<p class="toc level4"><a href="gipgl.html#gkcki">Outbound and Inbound Contracts</a></p>
<p class="toc level3 tocsp"><a href="girdd.html">Metadata Annotations</a></p>
<p class="toc level3"><a href="gipju.html">Common Client Interface</a></p>
<p class="toc level3"><a href="bncjw.html">Further Information about Resources</a></p>
<p class="toc level2 tocsp"><a href="bncdq.html">45.&nbsp;&nbsp;Java Message Service Concepts</a></p>
<p class="toc level2"><a href="bncgv.html">46.&nbsp;&nbsp;Java Message Service Examples</a></p>
<p class="toc level2"><a href="gkahp.html">47.&nbsp;&nbsp;Advanced Bean Validation Concepts and Examples</a></p>
<p class="toc level2"><a href="gkeed.html">48.&nbsp;&nbsp;Using Java EE Interceptors</a></p>
<p class="toc level1 tocsp"><a href="gkgjw.html">Part&nbsp;IX&nbsp;Case Studies</a></p>
<p class="toc level2"><a href="gkaee.html">49.&nbsp;&nbsp;Duke's Tutoring Case Study Example</a></p>
<p class="toc level1 tocsp"><a href="idx-1.html">Index</a></p>
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<a name="bncjj"></a><h2><tt>DataSource</tt> Objects and Connection Pools</h2>
<p><a name="indexterm-2280"></a>To store, organize, and retrieve data, most applications use a relational database. Java
EE 6 components may access relational databases through the JDBC API. For information
on this API, see <a href="http://www.oracle.com/technetwork/java/javase/tech/index-jsp-136101.html">http://www.oracle.com/technetwork/java/javase/tech/index-jsp-136101.html</a>.</p>

<p><a name="indexterm-2281"></a><a name="indexterm-2282"></a><a name="indexterm-2283"></a>In the JDBC API, databases are accessed by using <tt>DataSource</tt> objects. A <tt>DataSource</tt> has
a set of properties that identify and describe the real-world data source that
it represents. These properties include such information as the location of the database
server, the name of the database, the network protocol to use to communicate
with the server, and so on. In the GlassFish Server, a data source
is called a JDBC resource.</p>

<p><a name="indexterm-2284"></a>Applications access a data source by using a connection, and a <tt>DataSource</tt>
object can be thought of as a factory for connections to the particular
data source that the <tt>DataSource</tt> instance represents. In a basic <tt>DataSource</tt> implementation, a call
to the <tt>getConnection</tt> method returns a connection object that is a physical connection
to the data source.</p>

<p>A <tt>DataSource</tt> object may be registered with a JNDI naming service. If so,
an application can use the JNDI API to access that <tt>DataSource</tt> object, which
can then be used to connect to the data source it represents.</p>

<p><a name="indexterm-2285"></a><tt>DataSource</tt> objects that implement connection pooling also produce a connection to the particular
data source that the <tt>DataSource</tt> class represents. The connection object that the
<tt>getConnection</tt> method returns is a handle to a <tt>PooledConnection</tt> object rather than being
a physical connection. An application uses the connection object in the same way
that it uses a connection. Connection pooling has no effect on application code
except that a pooled connection, like all connections, should always be explicitly closed.
When an application closes a connection that is pooled, the connection is returned
to a pool of reusable connections. The next time <tt>getConnection</tt> is called, a
handle to one of these pooled connections will be returned if one is
available. Because connection pooling avoids creating a new physical connection every time one is
requested, applications can run significantly faster.</p>

<p>A JDBC connection pool is a group of reusable connections for a
particular database. Because creating each new physical connection is time consuming, the server maintains
a pool of available connections to increase performance. When it requests a connection,
an application obtains one from the pool. When an application closes a connection,
the connection is returned to the pool.</p>

<p>Applications that use the Persistence API specify the <tt>DataSource</tt> object they are
using in the <tt>jta-data-source</tt> element of the <tt>persistence.xml</tt> file:</p>

<pre>&lt;jta-data-source>jdbc/MyOrderDB&lt;/jta-data-source></pre><p>This is typically the only reference to a JDBC object for a
persistence unit. The application code does not refer to any JDBC objects.</p>


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